GENETIC AND FUNCTIONAL ANALYSIS OF SYNAPTIC TRANSMISSION

了解神经元电信号机制的一个经典方法是使用果蝇的温度敏感(TS)麻痹突变体。这些突变体在允许的温度下正常发育，并可以转移到限制性温度来检测特定基因产物的生理功能。果蝇是这一目的的理想选择，因为它是放热的，易于进行复杂的遗传、分子、生化、电生理和行为分析。我们以前的工作通过检测昏迷(Comt)基因产物在突触传递中的作用，扩展了一些关于TS麻痹突变体的早期研究。我们的分析表明，comt基因产物dNSF1在启动停靠的小泡以快速、钙触发的胞吐中发挥作用。为了扩大我们对突触机制的研究，我们对影响突触传递的新突变进行了基因筛查，包括筛选COMT的遗传修饰物。COMT的一个增强子是钙通道α1亚单位基因Cacophony(CAC)的TS麻痹等位基因。突触生理学研究表明，CAC基因产物代表主要的钙通道α1亚单位，负责神经肌肉突触的递质释放。拟议的实验将利用在cacTS2修饰物的遗传筛选中恢复的一些新突变。CacTS2的快速TS麻痹表型，以及电压门控钙通道在神经递质释放中的中心作用，为我们扩展突触传递的遗传分析提供了另一个中心起点。我们对cacTS2基因修饰物的筛选非常成功，结果恢复了新的CAC等位基因和在突触传递中起作用的其他基因的基因外突变。拟议的实验将利用这一筛选的成功，进一步对CAC编码的钙通道在突触传递中的功能和相互作用进行遗传分析。

A classical approach to understanding the mechanisms of electrical signaling in neurons has been the use of temperature- sensitive (TS) paralytic mutants of Drosophila. These mutants develop normally at permissive temperature and can be shifted to restrictive temperatures to examine the physiological function of a specific gene product. Drosophila is ideal for this purpose given that it is exothermic and amenable to sophisticated genetic, molecular, biochemical, electrophysiological, and behavioral analysis. Our previous work has extended some early studies on TS paralytic mutants by examining the role of the comatose (comt) gene product in synaptic transmission. Our analysis has shown that the comt gene product, dNSF1, functions in the priming of docked vesicles for fast, calcium-triggered exocytosis. To broaden our investigation of synaptic mechanisms, we have conducted genetic screens for new mutations affecting synaptic transmission, including a screen for genetic modifiers of comt. One enhancer of comt is a TS paralytic allele of a calcium channel alpha1 subunit gene, cacophony (cac). Synaptic physiology in this mutant, termed cacTS2, shows that the cac gene product represents the primary calcium channel alpha1 subunit responsible for transmitter release at neuromuscular synapses. The proposed experiments will advantage of a number of new mutants recovered in a genetic screen for modifiers of cacTS2. The rapid TS paralytic phenotype of cacTS2, as well as the central role of voltage-gated calcium channels in neurotransmitter release, have provided another central starting point from which to expand our genetic analysis of synaptic transmission. Our screen for genetic modifiers of cacTS2 has been highly successful, resulting in the recovery of both new cac alleles and extragenic mutations in other genes functioning in synaptic transmission. The proposed experiments will capitalize on the success of this screen to pursue further genetic analysis of the functions and interactions of cac-encoded calcium channels in synaptic transmission.